PURPOSE: To assess the feasibility and safety of using cooled-tip electrodes to increase the volume of coagulation necrosis obtained or reduce the number of treatment sessions necessary with percutaneous tumor radio-frequency (RF) ablation. MATERIALS AND METHODS: Twenty-nine patients with 44 hepatic metastases (1.3-5.1 cm diameter) from colorectal (n = 22), gastric (n = 5), pancreatic (n = 1), or breast (n = 1) carcinoma were treated with RF ablation using cooled-tip, 18-gauge electrodes with 2-3 cm tip exposure. Each tumor was treated in one or two treatment sessions. RESULTS: Technical success, ablation of all visualized tumor, was achieved in 40 (91%) metastases. Findings at computed tomography (CT) and magnetic resonance (MR) imaging performed 3-6 months after treatment confirmed complete necrosis of the entire metastasis in 66%. Disease-free survival was 50% at 12 months and 33% at 18 months, with localized progression of disease in 34% of treated lesions. Overall survival was 100%, 94%, and 89% at 6, 12, and 18 months, respectively. Only one complication, self-limited hemorrhage, was seen. CONCLUSION: Use of cooled-tip electrodes was a safe and feasible adjunct for tumor RF ablation therapy that produced larger volumes of coagulation necrosis with fewer electrode insertions than is produced with other RF ablation techniques.